Abela Laser Systems proposes to design, develop and characterize a combination Laser-Electrode Catheter designed specifically for Percutaneous Transvenous AV Node-His Bundle Ablation. The catheter will be capable of safely projecting a sufficient amount of laser energy to the AV Node-His Bundle to ablate or permanently modify the conduction characteristics of that tissue. This system would find immediate application to the treatment of patients suffering from Superventricular Arrythmias which do not respond to pharmacologic therapy. The Phase I goals include the further development of a proven design, the characterization of the resulting device in -vitro on fresh cadaveric myocardium and valve tissues, and in-vivo application in a canine model. All in-vitro and in-vivo testing will be performed by a medical research facility with a background in catheter-based laser medicine. The ALS AV Node-His Bundle Lase Ablation Catheter would provide the first tool for precise, controlled modification or abolition of AV nodal conduction.